1. Field of the Invention
The present invention relates to mid-mount type tiding lawn tractors, and more particularly to a structure for connecting a mower unit to tractor frames.
2. Description of the Related Art
One example of structure for connecting a mower unit to a tiding lawn tractor is disclosed in Japanese Utility Model Publication Kokai No. 63-26221.
This connection structure includes support arms extending rearward from lower forward positions of tractor frames to be vertically pivotable about a transverse axis. The support arms are connected at rear ends thereof to rearward positions of the mower unit. Forward positions of the mower unit are pivotally connected to the tractor frames through interconnected links, respectively. One of the links defines a slot for receiving a pin fixed to one of the support arms, so that this link is movable and pivotable relative to the support arm within a range provided by the slot. When the support arms are moved vertically, the mower unit makes a vertical parallel movement by action of the support arms and interconnected links. That is, according to the above structure, when the support arms are moved vertically, the pins of the support arms move within the slots formed in the links. The links are movable and pivotable relative to the support arms to absorb a difference between loci of movement of the supports arm and links.
However, in the structure in which the pins of the support arms move within the slots of the links, local wear is developed where the slots and pins contact each other after a long period of use. As a result, the pins become substantially inclined relative to the slots to cause a twist or jam, impairing movement of the pins in the slots.
Moreover, a riding lawn tractor scatters large quantities of grass clippings, soil and the like around the mower unit during an operation. Such grass clippings, soil and the like may enter the slots to increase the chance of twisting or jamming, thereby making a smooth vertical movement of the mower unit impossible.